Interleaver, deinterleaver, communication device, and method for interleaving and deinterleaving

ABSTRACT

A communication device carries out communication using N number of communication channels, where N is an integer not less than 2. The communication device includes interleavers that shuffle a data series, which is meant to be transmitted over the N number of communication channels, in at least two directions from among a time direction, a space direction, and a frequency direction, and deinterleavers that shuffle the data series back to obtain the original data series.

This application is a Divisional of Prior application Ser. No.11/023,963 filed Dec. 29, 2004 and claim benefit of the applicationunder 35 U.S.C. § 120.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to an interleaver and a deinterleaver thatrespectively shuffle data and restore the order of data in acommunication system. More particularly, the present invention relatesto an interleaver, a deinterleaver, a communication device, and a methodfor trans-communication channel interleaving and deinterleaving, bywhich data can be sorted across a plurality of communication channels.

2) Description of the Related Art

A communication device deployed in a conventional communication systemis explained first. Error bursts due to fading are common incommunication systems like wireless LAN802.11 or HISWAN, etc. To counterthe error bursts, these communication systems perform bit interleavingon the data that is subjected to an error correction coding. To bespecific, an interleaver at the transmitter end shuffles the order ofthe data that is subjected to error correction coding, while adeinterleaver at the receiver end restores the original order of thedata. The processes of interleaving and deinterleaving randomize theoccurrence of burst errors and reduce data error.

A conventional communication system stipulated by the wireless LANstandards 802.11a set down by the United States (see Institute ofElectrical and Electronic Engineers (IEEE) Standards 802.11a-1999) isexplained next. The transmitter at the transmitting end subjects theinformation data to error correction coding, and shuffles the order ofthe data (conventional method of interleaving). The transmitter furthermodulates the shuffled data by a predetermined modulation method, andtransmits the data. At the receiver end, the modulated data isdemodulated, and the original order of the data is restored, after whichthe data is decoded.

However, the communication device in the conventional communicationsystem has the following problems.

FIG. 8A and FIG. 8B are drawings illustrating an interleaving methoddeployed in the conventional communication system.

Specifically, FIG. 8A represents a Binary Phase Shift Keying (BPSK)interleaver that shuffles data by writing horizontally and readingvertically. FIG. 8B represents a Quadrature Phase Shift Keying (QPSK)interleaver, which also shuffles data like the BPSK interleaver, thatis, by writing horizontally and reading vertically. The size and theshape of the interleaver created are specific to the modulation method,and closing of the interleaving process is independent of thecommunication channel.

However, in a communication involving a plurality of communicationchannels, if the interleavers are closed independently in all thecommunication channels as in the conventional communication system,deterioration in communication conditions in one of the communicationchannels (that is, if one of the communication channels is affected byinterference, etc.) leads to a significant reduction in the throughput.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least solve the problemdescribed above, and to provide an interleaver, an deinterleavercorresponding to the interleaver, and a communication device thatincludes the interleaver and the deinterleaver that shuffle data acrossa plurality of communication channels, and maintain a high throughput byaveraging out the communication conditions of each of the communicationchannels.

To solve the above problem, and to achieve the objective mentionedabove, an interleaver provided in a communication device that carriesout communication using N number of communication channels, where N isgreater than 2, includes a trans-communication channel interleaving unitthat shuffles a data series to be transmitted to the N number ofcommunication channels, in at least two directions from among a timedirection, a space-division communication channel direction, and afrequency-division communication channel direction.

According to the present invention, a data series in the form of anoutput of a single error correcting encoder is transmitted bydistributing the output to a plurality of frequency-divisioncommunication channels. Consequently, even if one communication channelis unable to communicate independently due to a sudden majorinterference, or the like, the errors are widely scattered due to thetrans-communication channel interleaving, and therefore, errorcorrection can be carried out.

According to the present invention, a data series meant for transmissionis transmitted to a plurality of frequency-division communicationchannels. Consequently, even if one communication channel is unable tocommunicate independently due to a sudden major interference, or thelike, the errors are widely scattered due to the trans-communicationchannel interleaving and deinterleaving. As a result, error correctioncan be carried out, and throughput is not adversely affected.

The other objects, features, and advantages of the present invention arespecifically set forth in or will become apparent from the followingdetailed description of the invention when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are drawings of a communication device in which aninterleaver and a deinterleaver according to the present invention aredeployed;

FIG. 2A and FIG. 2B are drawings of configurations of the interleaverand deinterleaver;

FIG. 3A and FIG. 3B are drawings illustrating an example of a shufflingmethod;

FIG. 4A and FIG. 4B are drawings illustrating another example of theshuffling method;

FIG. 5 is a drawing of a configuration of a communication system inwhich the communication device shown in FIG. 1 uses MIMO communicationchannels;

FIG. 6A and FIG. 6B are drawings illustrating yet another example of theshuffling method;

FIG. 7 is a drawing illustrating yet another example of the shufflingmethod; and

FIG. 8A and FIG. 8B are drawings illustrating an interleaving methoddeployed in a conventional communication system.

DETAILED DESCRIPTION

Exemplary embodiments of the interleaver, the deinterleaver, thecommunication device, and the method of interleaving and deinterleavingaccording to the present invention are explained next with reference tothe accompanying drawings. The present invention is not limited to theembodiments described herein.

First Embodiment

FIG. 1A and FIG. 1B are drawings of a communication device in which theinterleaver and the deinterleaver according to the present invention aredeployed. To be more specific, FIG. 1A is a drawing of the communicationdevice at a transmitter end, and FIG. 1B is a drawing of thecommunication device at a receiver end.

The communication device according to the present embodiment is assumedto have N number of frequency-division communication channels. Thetransmitter end communication device shown in FIG. 1A includes M numberof error correcting encoders 1-1 through 1-M, an interleaver 2 thatshuffles the data meant for different communication channels, and Nnumber of modulating units 3-1 through 3-N. The receiver endcommunication device shown in FIG. 1B includes N number of demodulatingunits 4-1 through 4-N, a deinterleaver 5 that shuffles the data meantfor different communication channels, and M number of error correctingdecoders 6-1 through 6-M.

The error correcting encoders 1-1 through 1-M perform a predeterminedencoding process on the data meant for transmission (transmission data).The interleaver 2 shuffles the outputs from M number of error correctingencoders 1-1 to 1-M (that is, performs interleaving between the outputsfrom the plural error correcting encoder). Each of the modulating units3-1 through 3-N modulates the shuffled transmission data by apredetermined modulation method assigned to the relevant communicationchannel, and outputs the modulated transmission data. Each of thedemodulating units 4-1 through 4-N of the receiver end transmissiondevice demodulates the receiver signal of the relevant communicationchannel. The deinterleaver 5 shuffles the data back to the originalorder of the data (that is, restores the order of the data) shuffled bythe interleaver 2. Each of the error correcting decoders 6-1 through 6-Mdecodes the original transmission data by a decoding methodcorresponding to the relevant error correcting encoders 1-1 through 1-M.

FIG. 2A is a drawing of a configuration of the interleaver according tothe present invention, and FIG. 2B is a drawing of a configuration ofthe deinterleaver according to the present invention. The interleaveraccording to the present invention includes a distributing unit 11, andN number of interleaving units 12-1 through 12-N. The deinterleaveraccording to the present invention includes N number of deinterleavingunits 13-1 through 13-N, and a distributing unit 14.

The distributing unit 11 distributes the outputs from M number of errorcorrecting encoders 1-1 through 1-M among N number of interleaving units12-1 through 12-N. The distributing unit 11 distributes, by apredetermined distribution method, the outputs from M number of errorcorrecting encoders to each interleaving unit. The N number ofdeinterleaving units 13-1 through 13-N shuffle the data back to restoreits original order. The distributing unit 14 has an action that is thereverse of the distributing unit 11, that is, distributes outputs fromthe N number of deinterleaving units 13-1 through 13-N among M number oferror correcting decoders 6-1 through 6-M.

FIG. 3A and FIG. 3B are drawings illustrating an example of a shufflingmethod according to the present embodiment. To be more specific, FIG. 3Ais a drawing illustrating a process of writing to the interleaving unitswhen M=2 and N=2. FIG. 3B is a drawing illustrating the outputs of theinterleaving units.

It is assumed that a first communication channel corresponding to theinterleaving unit 12-1 employs BPSK as the modulation method, and asecond communication channel corresponding to the interleaving unit 12-2employs QPSK as the modulation method, and that both the interleavingunits 12-1 and 12-2 conform to the Wireless LAN Standard 802.11a. Inother words, the interleaving unit 12-1 is assumed to employ themodulation method shown in FIG. 8A, and the interleaving unit 12-2 isassumed to employ the modulation method shown in FIG. 8B. Theinterleaving units that conform to standards or systems other thanWireless LAN 802.11a may also be used. In the example, both M and N aretaken as 2. However, M may be any number equal to or more than 1, and Nmay be any number equal to or greater than 2, and if these conditionsare fulfilled, M may be equal to, less than or greater than N. Themodulation method of the communication channel is not limited to BPSKand QPSK, and may be any multiple value modulation.

The non-shaded numbers in FIG. 3A represent the output (for instance,bits) of the error correcting encoder 1-1, and the shaded numbersrepresent the output of the error correcting encoder 1-2. It is assumedin this example that the number of symbols transmitted by the firstcommunication channel and the second communication channel is the same.However, because twice as much data can be sent by QPSK as by BPSK, theoutput of the interleaving unit 12-2 is twice that of the interleavingunit 12-1.

In the distributing unit 11, the outputs from the error correctingencoders 1-1 and 1-2 are written alternately starting from the rows,with the write numbers corresponding to the interleaving unit 12-1 (rowwith the write number 1) and the interleaving unit 12-2 (row with thewrite number 2) in the sequence of the write numbers (1 through 9). Inthis way, one-third of the output of the error correcting encoders 1-1and 1-2 is written to the interleaving unit 12-1, and the remainingtwo-thirds is written to the interleaving unit 12-2. Because the outputsfrom the interleaving units 12-1 and 12-2 are read column-by-column, anintermingled output of the error correcting encoder 1-1 and the outputof the error correcting encoder 1-2 emerge as the outputs from theinterleaving units 12-1 and 12-2, as shown in FIG. 3B.

FIGS. 4A and 4B are drawings illustrating another example of theshuffling method according to the present embodiment. To be morespecific, FIG. 4A is a drawing illustrating a process of writing to theinterleaving units when M=2 and N=2. FIG. 4B is a drawing illustratingthe outputs of the interleaving units. The conditions for shuffling arethe same as described with reference to FIG. 3A and FIG. 3B.

In the distributing unit 11, the outputs from the error correctingencoders 1-1 and 1-2 are written alternately between the interleavingunits 12-1 and 12-2, one bit each from the error correcting encoders 1-1and 1-2 for the interleaving unit 12-1, and two bits each from the errorcorrecting encoders 1-1 and 1-2 for the interleaving unit 12-2. Thisprocess is carried out until all the three rows are filled in theinterleaving unit 12-1, and all the six rows are filled in theinterleaving unit 12-2. Thus, bits from the error correcting encoders1-1 and 1-2 are shuffled in a different way than that shown withreference to FIG. 3A and FIG. 3B.

In the present embodiment, the first communication channel and thesecond communication channel are assumed to have the same number oftransmission symbols. However, the number of transmission symbols in thetwo communication channels may be different. Further, the distributionof the bits to the interleaving units may not be equal. Moreover, anydistribution method may be used, as long as the bits that are written tothe interleaving units are reasonably shuffled.

Thus, in the present embodiment, a data series in the form of an outputof a single error correcting encoder is transmitted by distributing theoutput to a plurality of frequency-division communication channels.Consequently, even if one communication channel is unable to communicateindependently due to a sudden major interference, or the like, theerrors are widely scattered due to the trans-communication channelinterleaving and deinterleaving, and the error correcting decoders areable to carry out error correction. As a result, throughput is notadversely affected. Because the interleaver 2 consists of thedistributing unit 11 and the interleaving units 12-1 through 12-N, theconventional interleaver, which is modulation method-specific, may alsobe adaptable.

The communication in the communication device according to the presentinvention is explained with reference to a plurality offrequency-division communication channels. However, the presentinvention is not limited thereto, and a plurality of space-divisioncommunication channels (Multiple-Input Multiple-Output (MIMO)communication channels, corresponding to communication channels 7-1,7-2, and so on through 7-N shown in FIG. 5) may also be used. FIG. 5 isa drawing of a configuration of a communication system in which thecommunication device shown in FIG. 1 uses MIMO communication channels.Thus, if the shuffling method according to the present embodiment isdeployed, the effect described earlier can be achieved even with MIMOcommunication channels. The MIMO communication channels may be realizedby a plurality of antennae, or by beam forming, as long as they usespace-division.

Further, in the present embodiment, the same effect described earliercan be achieved by using a plurality of both frequency-divisioncommunication channels and time-division communication channels (MIMOcommunication channels) for communication.

FIG. 6A and FIG. 6B are drawings illustrating yet another example of theshuffling method of the interleaver 2 according to the presentembodiment. To be specific, FIG. 6A and FIG. 6B are drawingsillustrating shuffling in frequency direction and space direction.

FIG. 6A is a drawing illustrating an output sequence when no shufflingis carried out by the interleaver. FIG. 6B is a drawing illustrating theoutput sequence after the interleaver performs interleaving. In thisexample, the communication channel is assumed to have four rows in thespace direction and three columns in the frequency direction. However,there may be greater or fewer rows and columns.

In the shuffling method explained with reference to FIG. 6A and FIG. 6B,the conventional time-direction interleaving unit may be jointly usedeither by connecting it in the beginning or at the end.

FIG. 7 is a drawing illustrating yet another example of the shufflingmethod of the interleaver 2 according to the present invention. To bespecific, FIG. 7 is a drawing illustrating an output order of the dataprior to interleaving shown in FIG. 6A, after it is shuffled infrequency direction, space direction, and time direction. In thisexample, the communication channel is assumed to have four rows in thespace direction and three columns in the frequency direction. However,there may be greater or fewer rows and columns.

The interleaver described in the claims is essentially equivalent to theinterleaver 2 described in the present embodiment, and a plurality ofinter-communication channel interleaving units described in the claimsare essentially equivalent to both the interleaver described in theclaims and the interleaver 2.

Although the invention has been described with respect to a specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

1. A communication method for a transmitter that transmits transmissiondata to a receiver using a plurality of frequency-dividedtrans-communication channels, the method comprising, a shuffling stepfor shuffling the transmission data in a time direction and afrequency-divided communication channel direction.
 2. The communicationmethod according to claim 1, wherein the shuffling step includes: a timedirection shuffling step that shuffles the transmission data in the timedirection; and a frequency direction shuffling step that shuffles thetransmission data in the frequency-divided communication channeldirection.
 3. The communication method according to claim 1, wherein themethod further comprises, an encoding step that encodes the transmissiondata before the transmission data is inputted to the shuffling step. 4.A communication method for a receiver that receives transmission datatransmitted from a transmitter, wherein the transmitter shuffles thetransmission data in a time direction and a frequency-dividedcommunication channel direction in accordance with a predetermined firstshuffling process, the method comprises, a restoring step that restoresthe transmission data by conducting a second shuffling process that is areverse of the first shuffling process.
 5. A transmitter that transmitstransmission data to a receiver using a plurality of frequency-dividedtrans-communication channels, the transmitter comprising, a shufflingunit that shuffles the transmission data in a time direction and afrequency-divided communication channel direction.
 6. The transmitteraccording to claim 5, wherein the shuffling unit includes: a timedirection shuffling unit that shuffles the transmission data in the timedirection; and a frequency direction shuffling unit that shuffles thetransmission data in the frequency-divided communication channeldirection.
 7. The receiver according to claim 5, wherein the receiverfurther comprises, an encoding unit that encodes the transmission databefore the transmission data is inputted to the shuffling unit.
 8. Acommunication system comprising: a transmitter configured to shuffletransmission data in a time direction and in directions of a pluralityof frequency-divided communication channels in accordance with a firstshuffling process predetermined, and to transmit the transmission datausing the plurality of frequency-divided communication channels; areceiver configured to receive the transmission data transmitted fromthe transmitter; and a restoring unit configured to restore thetransmission data by conducting a second shuffling process which is areverse of the first shuffling process.